This invention relates to an automatic analyzing apparatus for automatically effecting chemical analyses for various sample fluids such as (but not limited to): cerebrospinal fluid, blood, urine, and the like.
Automatic chemistry analyzers can be roughly divided into two broad categories: continuous flow or discrete systems. Presently the majority of analyzer models employ the discrete approach to automation.
In a discrete system, each test is carried through the analytical process in its own dedicated (discrete) container or compartment. Current discrete analyzers can be further classified into two major sub-categories; sequential and centrifugal analyzers.
In sequential testers, all tests are performed sequentially, one after another, so that at any given point in time all tests in process are in a somewhat different stage of progress. In general, sample and reagent are metered into a vessel which is fed along a given path and the test liquids in each of the vessels are treated to each aspect of the analysis (reagent addition, mixing, quantitating, etc.) in sequence.
Centrifugal analyzers are also discrete but test liquids are processed in parallel to one another. All samples in process are in the same state of analysis at the same time. In operation, samples and reagent are pre-measured and pre-loaded into appropriate compartments arranged about the circumference of a rotor disc, whereupon it is placed on a centrifuge and rotated at a high speed past a photometer device. Centrifugal force mixes all samples with reagent at the same time and hence each of the test liquids is in the same stage of analysis at any given point in time.
The majority of analyzers, regardless of the above mentioned categories, are capable of performing more than one type of test item. There are three broad categories of methods for providing for multi-test capability.
What shall hereinafter be referred to as Random Access Testers currently require individual test packs which are pre-packaged with the appropriate reagents required to perform one test of a given test type. These test packs are loaded into the instrument system according to the analyst's needs, charged with a sample liquid, and processed in a discrete manner. Random access testers offer great convenience and flexibility but currently available embodiments have low productivities when compared with other means of providing multi-test item capability. In addition, the requirement for pre-packaged test packs makes operating costs much higher than the alternate methods.
Another means of performing a plurality of tests on each of a plurality of samples is sequentially by test-item batch. All samples are analyzed sequentially or centrifugally for a given test item. When all samples have been analyzed for a given test item, the system is changed over, or somehow modified, to perform a different test item and all appropriate samples are re-treated. When all samples have been processed for the required test items, the results of each samples' test items must be collated to allow including all of a given samples analytical results on a single report form for return to a physician, etc. Such systems are usually referred to as `single channel` systems. Single channel systems are usually considered most appropriate for treating a batch or plurality of samples, as the effort required to change-over from one test item to another is generally neither convenient nor cost-effective to treat one sample for a plurality of test items. Additionally, at any given moment in time, only one test item is available for immediate use.
Simultaneous analyzers have a plurality of analytical channels which enable a plurality of test items to be performed simultaneously on each sample. Such systems are commonly referred to as `multi channel` analyzers. Mult-channel analyzers do make more than one test item available at any given point in time, do eliminate the data collating task required of single channel analyzers and in general, do have higher productivities than single-channel analyzers by virtue of the fact that they are constructed as a plurality of single-channel analyzers combined into one device. This last feature is a drawback in that it makes the analyzer system complicated in construction, large in size, and generally, much higher in cost than single-channel discrete, continuous flow or centrifugal analyzers.
In the known analytical systems of the non-centrifugal type, photometric quantitation is carried out after some time period from the initiation of the test reaction, i.e. when the test liquid has travelled along the processing line by some given fixed distance. Therefore, the reaction time is fixed as a function of the length or circumference of the processing line, which may or may not be optimal with respect to a given test item and/or sample.
Additionally, sequential testers have only one photometer position per channel, severely limiting the amount of photometric data which can be made available. No photometric data can be made available until a test liquid reaches the photometer station, typically, 8-10 (often 30) minutes from the time of mixing of sample with reagent. Once a test liquid reaches a photometer station, the amount of time which is devoted to photometric measurement essentially limits the speed of analysis of a given sequential tester, i.e. if 60 seconds is devoted to photometric quantitation, then the processing rate is limited to 60 tests per hour. This feature forces a trade-off between processing rate and photometric quantitation time especially for `kinetic` test (ex. enzyme rate tests) which require photometric measurement over long periods of time in order to provide for best accuracy and precision of analysis.